In rotary electric machines, the presence of induced electric current is known and is usually found in three-phase motors driven by frequency converters.
Said converters use pulse-width modulation technology to vary the speed of AC machines, thus allowing the use of lower cost AC motors in applications wherein DC motors were used, which are currently more expensive. The main disadvantage of the use of three-phase motors with frequency converters is that the common-mode voltage generated by the converter increases the induced currents in the electric machine rotor.
Therefore, there is the emergence of current flow through the bearings to the motor housing where such a current finds the grounding. While the engine is running, the bearings tend to become more resistant to the current flow, causing an electrical charge buildup on the surfaces of the rotor.
During a short period, the common-mode voltage produces high-level electric charges and, as a result, such charges overcome the electrical resistance imparted by the bearing and an instantaneous arc passes through said bearing. This discharge causes an electroerosion in the component, which can damage the surfaces of the bearing tracks and the bearing balls. This phenomenon reduces the lifespan of the bearing, which may imply premature failure of the same.